This invention relates to an electrophotographic member and a fluorine-containing N,N,N',N'-tetraarylbenzidine derivative usable as a charge transport material in the electrophotographic member.
Heretofore, electrophotographic members containing inorganic materials such as Se, CdS, etc. have been used mainly, but recently electrophotographic members using organic materials are noticed from the viewpoints of safety in handling and advantage in price. Electrophotographic members can be divided into a single layer type wherein a charge generation material and a charge transport material are present in a single layer, and a laminated type wherein a charge generation layer and a charge transport layer are laminated.
As charge transport materials, there are known charge transport materials having electron transport ability such as a mixture of polyvinyl carbazol and trinitrofluorenone (1:1 by mole), and charge transport materials having hole transport ability such as hydrazones, enamines, benzidine derivatives (Japanese Patent Examined Publication Nos. 55-42380 and 59-9049, Japanese Patent Unexamined Publication Nos. 62-237458, 55-79450, and 61-295558, U.S. Pat. Nos. 4,265,990; 4,306,008 and 4,588,666).
As the benzidine derivatives, there are known N,N,N',N'-tetraphenylbenzidine, N,N'-diphenyl-N,N'-bis(3-methylphenyl)-benzidine, N,N,N',N'-tetrakis(4-methylphenyl)-benzidine, N,N'-diphenyl-N,N'-bis(4-methoxyphenyl)-benzidine, etc. But, these benzidine derivatives are low in solubility in organic solvents and/or easily oxidized. Since these benzidine derivatives are low in solubility in organic solvents and/or binders, it is difficult to prepare a coating solution for forming a charge transport layer, and crystals of the benzidine derivatives are undesirably deposited at the time of forming the coating film. Further, even if a good charge transport layer can be formed, since resistance to oxidation of the benzidine derivatives are poor, there are defects in that charging characteristics, dark decay, sensitivity and image quality are lowered when used repeatedly.
As binders used in combination with these benzidine derivatives, there are known bisphenol A type polycarbonates (Japanese Patent Examined Publication No. 59-9049), poly(4,4'-cyclohexylidenediphenylenecarbonate) (Japanese Patent Unexamined Publication No. 63-278065), etc. But since these benzidine derivatives are poor in resistance to oxidation, there are defects in that charging characteristics, dark decay, sensitivity and image quality are remarkably lowered when used repeatedly. As charge generation materials used in combination with these benzidine derivatives, there are known chloroindium phthalocyanine (Japanese Patent Unexamined Publication No. 61-84655), vanadyl phthalocyanine (Japanese Patent Unexamined Publication No. 61-295558), but not sufficient in practical use in sensitivity.